The context is avs2yuv64.exe. It is avs2yuv-0.24bm5 - the last version.

When I use ffms2-2.23.1 as a source FFMS2(<"file_name.m2ts">, colorspace = "yuv420p10")
it works and the process displays the mesage:
encode-FFMS2.265.avs: 3840x2160, YUV420P10, 10-bits, progressive, 12500/473 fps, 3171 frames

The context is avs2yuv64.exe. It is avs2yuv-0.24bm5 - the last version.

When I use ffms2-2.23.1 as a source FFMS2(<"file_name.m2ts">, colorspace = "yuv420p10")
it works and the process displays the mesage:
encode-FFMS2.265.avs: 3840x2160, YUV420P10, 10-bits, progressive, 12500/473 fps, 3171 frames

Can you open your script encode-FRIM.265.avs directly using e.g. MPC-HC(x64) media player?
(You need to use some 64-bit media player which is capable to play Avisynth+ scripts. MPC-HC(x64) is able to do it).

If yes then script is correct and problem is somewhere in avs2yuv64.exe - this I cannot help...

MPC-HC(x64), AvsPmod too, can play the scripts.
When playing FFMS2("file_name.m2ts", colorspace = "yuv420p10") there is a normal 3640x2160 picture.
When playing FRIMSource(codec="h265", filename="file_name.m2ts", cache=1, num_frames=240) there is no picture.
with FRIMSource(codec="h265", filename="file_name.m2ts", cache=1, num_frames=240, container="ts")
there is the Error message above when I've tried .mkv file.

MPC-HC(x64), AvsPmod too, can play the scripts.
When playing FFMS2("file_name.m2ts", colorspace = "yuv420p10") there is a normal 3640x2160 picture.
When playing FRIMSource(codec="h265", filename="file_name.m2ts", cache=1, num_frames=240) there is no picture.
with FRIMSource(codec="h265", filename="file_name.m2ts", cache=1, num_frames=240, container="ts")
there is the Error message above when I've tried .mkv file.

As to "I'm not sure whether you read the first post of this thread
Free H.264 MVC 3D Encoder ..."
Sorry, I've missed the important part.

I've tried it and I would like to ask you some questions about:
(Better if there is a written instruction.)
- VBR - avg, maximum; obviously I can change them. But, working with x264, I prefer Constant QP with control over the maximum bitrate.
- are there other parameters avilable
- performance - with no more than 38% CPU load I've got 7 fps.